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Fully Operational System Modernizes for the Multi-GNSS World

Vitaly Davydov and Sergey Revnivykh

By Vitaly Davydov and Sergey Revnivykh

Since December 2011, the GLONASS system has been fully operational, providing worldwide service with 100 percent global availability and acceptable accuracy for most users. The system is globally accepted by many users, and most leading manufacturers include GLONASS in their devices.

This fact became a reality due to the successful completion in December 2011 of the Russian Federal Mission Oriented Program dedicated to GLONASS restoration, under the under permanent supervision and control of the President of the Russian Federation and Russian Government, Vladimir Putin.
It may have seemed back in 2002 that very few people outside the GLONASS team believed in the success of the Program, when the constellation was composed of six operational satellites with only a 3-year lifetime. But now the GLONASS constellation consists of 24 modernized operational Glonass-M satellites and in-orbit spares. Further, the new generation GLONASS-K satellite flight tests have begun.

The GLONASS Program obtained significant support in May 2007 when the famous Decree of the President of the Russian Federation was issued. The President made commitments to sustain the GLONASS system and provide its open service free of charge and available for all users worldwide without any restrictions. At the same time, the President charged the Government to prepare and approve the new GLONASS Program for 2020. The new Federal Mission Oriented Program ,designated GLONASS maintenance, development and use for 2012–2020, was approved by the Government of the Russian Federation on March 3, 2012 with a dedicated article in the State Budget Law. That means that the President’s commitments are supported by real financial resources for the next decade, and the situation of the mid-1990s will never occur to GLONASS again.

The new Program has three major tasks:

To keep GLONASS in full operational mode.

To significantly improve GLONASS performance and service quality.

To provide conditions for worldwide use.

The tasks to make GLONASS an integral component of the global GNSS infrastructure, providing worldwide service for all users, are challenging. At the same time, the primary goal of GLONASS as a dual-use system is to serve national security interests.

What the Future Brings

GLONASS development in the near future is foreseen in a few key directions.

Space Segment. Modernization of the GLONASS core, called the Space Complex, undertakes the development of new spacecraft with enhanced performance. This means more stable on-board clocks, new code-division multiple-access (CDMA) signals, and intersatellite link for orbit, clock update, and range measurements. The GLONASS-K satellite will be the new generation spacecraft, applying advanced technologies.

The first-phase GLONASS-K satellite is already passing flight tests, transmitting new CDMA signal in L3 band in addition to the existing set of FDMA signals. The GLONASS-K of the second modernization phase will transmit the full set of new CDMA signals in L1, L2 and L3 bands.

At the same time, all new GLONASS satellites will continue transmitting the existing set of frequency-division multiple-access (FDMA) signals, providing backward compatibility with existing user equipment. Implementation of the CDMA signals in L5 and in L1 (1575.42 MHz) bands is also in line with the Signal Modernization Concept. This task is undergoing study to optimize the power and mass budget of future satellites and to consider benefits for users. Finally, new CDMA signals will provide better accuracy, better protection to interference and better service for users.

GLONASS modernization foresees extending the number of operational satellites in constellation available for users. Presently navigation message enables maximum 24 satellites for users. Activities in order to get more operation satellites available, assumes modernization of the existing FDMA almanac. New almanac of CDMA signals has no limitations.

Ground Segment. Ground-control segment modernization will produce a monitoring-station network extension to provide global coverage, extension of the uplink-station network to provide more frequent updates of orbit and clock, and system clock modernization to make the system time scale more stable and better synchronized with UTC.

The new geodesy reference PZ-90.11 is already coordinated with the International Terrestrial Reference Frame (ITRF) at the centimeter level and shall be introduced soon.

Augmentation. The System for Differential Correction and Monitoring (SDCM) space-based augmentation system is dedicated to improving navigation services, providing integrity data and better accuracy for users. As a first phase, the service area of SDCM is over the Russian territory. For SBAS signal re-transmission, the three GEO communication satellites of the Luch system are equipped with navigation transponders. The first Luch-5A is already in orbit. The other two are scheduled for launch. Eventually the SDCM system will provide a global navigation service, transmitting precise orbit and clock data to users and introducing precise-point positioning (PPP) technique.

Performance Improvements. The GLONASS modernization plan foresees step-by-step performance improvement of all system components. By 2020, the GLONASS system in stand-alone mode will provide sub-meter accuracy for users with an open signal. Augmented by SBAS, the GLONASS system will provide user positioning accuracy at the decimeter level and better.

In the coming Multi-GNSS world, the GLONASS system must be one of the key components to benefit all users with reliable and accurate navigation, positioning, and timing services. To reach that goal, the international cooperation between system providers with feedback from all group of users is a mandatory condition. All global and regional navigation satellite systems must be compatible and interoperable. The International Committee on GNSS, established according to UN recommendation, plays a significant role for international cooperation aimed at achieving synergy in the navigation environment.

2013 is very important for GLONASS to demonstrate stability with improvement for all users around the world. All the necessary resources to achieve this are available, based on the long-term Federal Mission Oriented Program supported by the President and the Government of the Russian Federation.

Vitaly Davydov is the deputy head of the Federal Space Agency, Coordinator of the Program for GLONASS Sustainment, Development, and Use. He graduated from the Dzerzhinsky Military Academy and from the Russian Presidential Academy of National Economy and Public Administration with a Master‘s degree in Public and Municipal Administration. From 1997 to 2004 Vitaly Davydov supported the Russian Federation Security Council’s Office. Prior to that from 1975 to 1997 he occupied various positions in Russian Department of Defense’s Space Forces.

Sergey Revnivykh is deputy director general of the Central Research Institute of Machine Building, leading institute of Federal Space Agency, Head of PNT (Positioning, Navigation and Time) Analysis and Information Center. He is a member of the management of the Federal GLONASS Program. He received his Ph.D. degree from the Moscow Aviation Institute.